CUET · PHYSICS · PYQ PAPER 2023

A convex lens of focal length 30 cm is in contact with a concave lens of focal length 20 cm. Is the system working as a converging or diverging lens. What is the focal length of the combination

A Converging, 10 cm
B Diverging, 60 cm
C Plane sheet of glass, infinite
D Diverging, 40 cm

Verified Solution

Answer & Solution

Correct Answer

(B) Diverging, 60 cm

Step-by-step Solution

Detailed explanation

\( \frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2} \) \( \frac{1}{F} = \frac{1}{30 \, \text{cm}} + \frac{1}{-20 \, \text{cm}} \) \( \frac{1}{F} = \frac{2 - 3}{60 \, \text{cm}} = \frac{-1}{60 \, \text{cm}} \) \( F = -60 \, \text{cm} \) Diverging, 60 cm

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match List-I with List-II>

List-I	List-II
(A) Bandwidth	(I) information converted into electrical form and suitable for transmission
(B) Repeater	(II) Loss of strength of a signal while propagating through a medium
(C) Signal	(III) Range of frequencies over which communication system work
(D) Attenuation	(IV) Combination of receiver and transmitter

Choose the correct answer from the options given below:

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